Development and Validation of a PET/SPECT Radiopharmaceutical in Oncology

[18F]FDG-PET and [18F]MPPF-PET are brain biomarkers for the creatine transporter Slc6a8 loss of function mutation

Pathogenic variants in the creatine transporter gene SLC6A8, reported to represent 2% of all intellectual disabilities in males, result in a spectrum of behavioral abnormalities including developmental delay, intellectual disability, and deficit in speech. While at present there are no effective treatments available, preclinical development and testing of gene therapy and other approaches to increase brain creatine are being actively pursued. In studying a mouse model of the disorder, [18F]fluorodeoxyglucose ([18F]FDG)-based positron emission tomography (PET)/computed tomography (CT) was performed to assess brain glucose metabolism in wild type and creatine transporter mutant mice (Slc6a8-/y). The findings demonstrate marked differences in glucose metabolism in the brains of wild type and Slc6a8-/y mice. In conducting behavioral phenotyping studies, notable abnormalities in behavior in the murine model led to additional studies in serotonin-mediated activity. Serotonergic signaling differences were detected between wild type and Slc6a8-/y mice using 4-(2'-methoxyphenyl)-1-[2'-(N-2″-pyridinyl)-p-[18F]fluorobenzamido]ethylpiperazine ([18F]MPPF). These data demonstrate that [18F]FDG-PET and [18F]-MPPF-PET may serve as appropriate and sensitive biomarkers that could be used to assess the efficacy of not only new approaches in treating mutations of the creatine transporter SLC6A8 and their effectiveness in normalizing brain metabolism but also in enhancing our understanding of the mechanism of brain dysfunction that occurs in this complex brain disorder.

Polymeric nanoparticles in radiopharmaceutical delivery strategies

The potential applications of polymer nanoparticles (NPs) in the biomedical field have been the subject of extensive research. Radiopharmaceuticals that combine radionuclides and drugs using polymer nanoparticles (NPs) as carriers can be externally labelled, internally labelled or interfacially labelled with radionuclides at different sites. Consequently, they can be employed as delivery agents for a range of diseases. Currently, polymeric nanoparticles can deliver isotopes via active targeting, passive targeting and stimuli-responsive release systems. The objective is to deliver drugs and nuclides to the target site in an efficient manner, thereby maximizing efficacy and minimizing side effects. The development of drug release systems has the potential to address the growing social and economic challenges currently facing modern healthcare. This paper presents a detailed synthesis of the methods used to create polymer nanoparticles (NPs) and strategies for the targeted delivery of radiopharmaceuticals with radionuclides labelled at different locations. Additionally, the paper outlines the current progress of polymer NPs for use in imaging and therapeutic applications, as well as the future challenges that lie ahead in this field.

Development of a Novel 99mTc-Labeled Folate Derivative Containing Phenyl Isonitrile to Target Folate Receptor with Reduced Renal Uptake

The folate receptor has attracted much attention in the field of radiolabeled imaging agents due to the significant difference in its expression levels between tumor cells and most normal cells. However, the development of folate-based imaging agents has been limited by their high uptake in the kidney. In this study, to reduce the high renal uptake of radiolabeled folate-based tracers, a phenyl-isonitrile folate derivative (CNMBFA) was designed and labeled with technetium-99m. The complex obtained via the one-step kit labeling method had a high labeling yield (>95%) and high in vitro stability and hydrophilicity (log D7.4 = -1.72 ± 0.13). The results of the in vitro cell uptake and blocking studies and competitive binding experiments revealed that the [[99mTc]Tc-(CNMBFA)6]+ complex was specific for the folate receptor. Biodistribution and inhibition studies in KB tumor-bearing mice revealed moderate uptake and significant inhibition of the complex in tumors, whereas the renal uptake of [[99mTc]Tc-(CNMBFA)6]+ was significantly lower than that of previously reported tracers. Micro-SPECT/CT images further supported its ability to target the folate receptor for tumor imaging. Taken together, these results indicate that [[99mTc]Tc-(CNMBFA)6]+ is a potential tumor imaging agent that has good tumor-targeting properties with minimal radiation damage to the kidney.

Cell Model for Testing Pharmaceuticals Targeting Human PD-L1

The aim of this study was to create and evaluate a cell model designed for in vitro and in vivo testing of anti-human PD-L1 therapeutic and diagnostic agents' specificity.

Materials and Methods

Genetically modified cells expressing human PD-L1 (strain CT26-PD-L1) were obtained by retroviral transduction of murine CT26 carcinoma cells. PD-L1 gene activity was assessed by real-time PCR, and PD-L1 expression on cells was identified by flow cytometry. Cells were tested using recombinant single-domain human anti-PD-L1 antibodies (nanoantibodies) conjugated with radioisotopes 68Ga or 177Lu. Immunoreactive fraction and cell internalization of the radioconjugates were evaluated in vitro. For in vivo experiments CT26-PD-L1 cells were transplanted into mice, radioimmunoconjugates were injected 9-14 days later, in 1-48 h the tumors were retrieved and subjected to direct radiometry. Intact CT26 cells not expressing the antigen served as a control.

Results

CT26-PD-L1 strain of murine tumor cells expressing human membrane PD-L1 was created. When transplanted into intact BALB/c mice or sublethally irradiated F1(DBA×BALB/c) mice, these cells formed tumors. Thus, a significant advantage of the model was the possibility of in vivo testing of human PD-L1-affinity agents using animals under conventional vivarium conditions. When radioimmunoconjugates were administered to tumor bearing mice, radionuclides accumulated in tumors generated from the transplanted CT26-PD-L1 cells, but not CT26 cells. CT26-PD-L1 cells internalized anti-PD-L1 nanobodies in vitro. Due to a high density of target molecules, CT26-PD-L1 cells allowed both to confirm pharmaceuticals' specificity and to quantify the target-binding fraction of conjugates in a single test.

Conclusion

The created cells are the first genetically engineered cells designed to evaluate affinity of anti-human PD-L1 therapeutic and diagnostic agents in Russia. Test results confirmed the model suitability for in vitro and in vivo testing of the specificity of pharmaceuticals targeting human PD-L1.

[68Ga]Ga-FAPI-46 synthesis on a GAIA® module system: Thorough study of the automated radiolabeling reaction conditions

The influence of several parameters involved in the 68Ga radiolabeling of FAPI-46 was studied at the scale of the automated reaction. Among the buffers tested, HEPES 0.3 M pH 4 allowed both high radiochemical purity (RCP) and radiochemical yield (RCY), without prepurification of 68Ga but after final purification of [68Ga]Ga-FAPI-46 on a C18 cartridge. A longer reaction time did not show significant benefit on the RCP, while higher loads of FAPI-46 and gentisic acid as anti-radiolysis compound allowed better RCY.

Radiopharmaceuticals: A New Vista for Diagnosis and Treatment of Thyroid Cancer

Radiopharmaceuticals are in the diagnosis and treatment of cancerous and noncancerous diseases, and a hope for optimistic effort in the field of nuclear medicine. They play a crucial role in clinical nuclear medicine by providing a tool to comprehend human disease and create efficient treatments. A detailed analysis is provided regarding the crux of molecular imaging including PET and SPECT overview for the detection of cancers. For a specified understanding of radiation therapy, topics include ranging from the selection of radionuclide to its development and manufacture, and dosage requirements to establishing the importance of I- 131 Radiotherapy in thyroid cancer. In this review, we also discussed the current state of the art of nuclear medicine in thyroid cancer, including the role of radioiodine (RAI) therapeutic scans in the diagnosis of differentiated thyroid cancer. In addition, we established a brief outlook into the current status of the research in thyroid cancer and discussed the future directions in this field.

Fully Automated Radiosynthesis of [18F]mG4P027 for mGluR4 Imaging

Fluorine-18 labeled N-(4-chloro-3-(((fluoro-¹⁸F)methyl-d₂)thio)phenyl)picolinamide, [¹⁸F]mG4P027, is a potent positron emission tomography (PET) radiotracer for metabotropic glutamate receptor 4 (mGluR4). Our previous in vitro and in vivo evaluations have demonstrated that this tracer is promising for further translational studies. To automate the radiosynthesis of [¹⁸F]mG4P027, significant modifications were made to the manual process by carefully examining this process and addressing the root causes of the challenges associated with its automation. We successfully implemented its automated radiosynthesis using the TRACERlab FX2N module and consequently, obtained a high-purity radiolabeled [¹⁸F]mG4P027 in high yield, meeting the requirements for future human studies.

Preclinical development of ZED8, an 89Zr immuno-PET reagent for monitoring tumor CD8 status in patients undergoing cancer immunotherapy

BACKGROUND

ZED8 is a novel monovalent antibody labeled with zirconium-89 for the molecular imaging of CD8. This work describes nonclinical studies performed in part to provide rationale for and to inform expectations in the early clinical development of ZED8, such as in the studies outlined in clinical trial registry NCT04029181 [1].

METHODS

Surface plasmon resonance, X-ray crystallography, and flow cytometry were used to characterize the ZED8-CD8 binding interaction, its specificity, and its impact on T cell function. Immuno-PET with ZED8 was assessed in huCD8⁺ tumor-bearing mice and in non-human primates. Plasma antibody levels were measured by ELISA to determine pharmacokinetic parameters, and OLINDA 1.0 was used to estimate radiation dosimetry from image-derived biodistribution data.

RESULTS

ZED8 selectively binds to human CD8α at a binding site approximately 9 Å from that of MHCI making mutual interference unlikely. The equilibrium dissociation constant (K_D) is 5 nM. ZED8 binds to cynomolgus CD8 with reduced affinity (66 nM) but it has no measurable affinity for rat or mouse CD8. In a series of lymphoma xenografts, ZED8 imaging was able to identify different CD8 levels concordant with flow cytometry. In cynomolgus monkeys with tool compound ⁸⁹Zr-aCD8v17, lymph nodes were conspicuous by imaging 24 h post-injection, and the pharmacokinetics suggested a flat-fixed first-in-human dose of 4 mg per subject. The whole-body effective dose for an adult human was estimated to be 0.48 mSv/MBq, comparable to existing ⁸⁹Zr immuno-PET reagents.

CONCLUSION

⁸⁹Zr immuno-PET with ZED8 appears to be a promising biomarker of tissue CD8 levels suitable for clinical evaluation in cancer patients eligible for immunotherapy.

A practical guide to automating fluorine-18 PET radiochemistry using commercially available cassette-based platforms

This Tutorial Account aims to be a useful educational resource which describes how to automate fluorine-18 positron emission tomography (PET) radiochemistry using cassette-based automated radiosynthesis platforms.